Method for preparing metallic carbene-based catalysts for hydrosilylation of unsaturated compounds and resulting catalysts

ABSTRACT

The invention concerns an improved method for preparing catalysts for hydrosilylation reactions of compounds with ethylene or acetylene unsaturation (for example olefins or acetylene derivatives), in particular but not exclusively those involving polyorganosiloxanes (POS) bearing Si—H units and POS bearing Si-(ethylene or acetylene unsaturation) units. Said preparation corresponds to the following synthesis (I), wherein: A=B=carbon: T 1 , T 2 =cyclohexyl, t-butyl or methyl; T 3 , T 4 =H; DVTMS=divinyltetramethylsiloxane; t-BuOK=potassium tert-butylate; T.A=room temperature. The invention is characterised in that it consists in carrying out said synthesis in a single step by bringing together salt (III) above, Karstedt (IV) in the presence of a solvent (V) (THF) and a base (VI) (t-BuOK) at room temperature.

The invention relates to the preparation of catalysts forhydrosilylation reactions and especially for the hydrosilylation ofethylenically and/or acetylenically unsaturated compounds (for exampleolefins or acetylenic derivatives), in particular, but not limited to,those involving polyorganosiloxanes (POS) bearing Si—H units and POSsbearing Si-(ethylenic or acetylenic unsaturation) units.

Conventionally, hydrosilylation catalysts are platinum catalysts (U.S.Pat. No. 2,823,218, U.S. Pat. No. 2,970,150). In practice, to date, themajority of industrial hydrosilylation reactions are catalyzed withKarstedt solution, which consists of complexes of platinum in oxidationstate 0. The ideal general formula of the Karstedt complex isPt₂(tetramethyldivinylsiloxane)₃:

in which Me represents methyl.

The Karstedt complex is prepared by placing1,3-divinyltetramethyldisiloxane in contact with chloroplatinic acid(H₂PtCl₆), in the presence of NaHCO₃ and an aqueous-alcoholic solvent(isopropanol).

This common catalyst and its production are described in patent U.S.Pat. No. 3,775,452.

The unpublished patent application FR 99/15432 of Dec. 07, 1999discloses metallic complexes that are useful as hydrosilylationcatalysts, of formula:

in which:

-   R₃ represents a hydrogen atom; a (C₁–C₈)alkyl group; or-   a (C₃–C₈)cycloalkyl group optionally substituted with (C₁–C₄)alkyl;-   T₁ and T₂ are identical and represent (C₁–C₈)alkyl or    (C₃–C₈)cycloalkyl;-   R_(d) and R_(e) are identical and represent (C₁–C₈)alkyl or    (C₃–C₈)cycloalkyl,-   (preferably, T₁=T₂=R_(d)═R_(e)=methyl).

These Pt/carbene metallic complexes are obtained according to a two-stepmethodology illustrated by the following example:

1. Preparation of the Carbene:

2. Preparation of the Platinum Complex of Formula:

In step 1, a reaction medium is used comprising a carbene precursor: forexample, 1,3-dimethylimidazolinium iodide, a solvent system comprisingTHF and ammonia, and a base: NaH. After deprotonation and evaporation ofthe ammonia, a solution of carbene in THF is obtained.

In step 2, this carbene solution is mixed with a solution of platinicKarstedt complex. After reaction and various filtration, purification,concentration, washing and precipitation steps, a solid Pt/carbenecomplex is obtained.

This preparation method would profit from being simplified andoptimized, especially as regard the yield and the production efficiency,with a view to an industrial application.

U.S. Pat. No. 5,728,839 also discloses the two-step preparation ofmetallic/carbene complexes, from imidazolium, benzimidazolium,triazolium, tetrazolium or pyrazolium salts (for example iodide). Thecarbene is obtained in a first stage by placing the imidazolium,benzimidazolium, triazolium, tetrazolium or pyrazolium salt in contactwith a deprotonating base, NaH, dissolved in THF. In a second stage, themetallic (rhodium) complex is obtained by exchange between the carbeneand a metal/cycloolefin complex (for example adi(μ-chloro)bis(η⁴-1,5-cyclooctadiene)dirhodium).

With such a state of the art, one of the essential objectives of theinvention is to propose an improved and efficient process for preparingmetallic complexes of formula (I):

Another essential objective of the invention is to propose a process forpreparing metallic complexes of formula I, which is improved comparedwith the process described in the prior unpublished patent applicationFR 99/15432 in terms of simplification of methodology, increase in yieldand reduction in cost.

Another essential objective of the invention is to propose an improvedprocess for preparing metallic complexes of formula I used ashydrosilylation catalysts, these catalysts needing to be stable in thereaction medium, so as:

-   -   to product a selective catalytic activity of a high qualitative        and quantitative level, and    -   to limit the formation:        -   of undesirable side products resulting from isomerization            reactions of the olefinic double bond and/or of            hydrogenation reactions        -   and/or of side products that are the origin of entirely            undesired colorations.

Another essential objective of the invention is to propose ahydrosilylation process and in particular for the hydrosilylation ofethylenically and/or acetylenically unsaturated compounds, in thepresence of a catalyst comprising the metallic complex obtained by theabovetargeted process.

These objectives, among others, are achieved by the present invention,which relates firstly to a process for preparing metallic complexes offormula (I):

in which:

-   M represents a metal chosen from the metals of group 8 of the    Periodic Table as published in the Handbook of Chemistry and    Physics, 65th Edition, 1984–1985;-   X represents O, NR_(a) or CR_(f)R_(g);-   Y₁ and Y₂ represent, independently of each other, CR_(b)R_(c) or    SiR_(d)R_(e);-   R₁, R₂, R₃, R₄, R₅, R₆, R_(a), R_(b) and R_(c), which may be    identical or different, are chosen from a hydrogen atom; an alkyl    group; an acyl group; an aryl group optionally substituted with    alkyl; a cycloalkyl group optionally substituted with alkyl; and an    arylalkyl group in which the aryl portion is optionally substituted    with alkyl;-   R_(d) and R_(e) are independently chosen from alkyl; aryl optionally    substituted with alkyl; cycloalkyl optionally substituted with    alkyl; and arylalkyl in which the aryl portion is optionally    substituted with alkyl; or alternatively-   when Y₁ and Y₂ independently represent SiR_(d)R_(e), two groups    R_(d) linked to two separate silicon atoms together form a chain of    formula:    in which n is an integer from 1 to 3; X is as defined above; R and    R′, which may be identical or different, take any of the meanings    given above for R_(e), it being understood that, when n is 2 or 3,    only one silicon atom of said chain may be substituted with one or    two alkenyl or alkynyl groups; or alternatively when Y₁ and Y₂    independently represent SiR_(d)R_(e), two groups R_(d) linked to    separate silicon atoms together form a saturated hydrocarbon-based    chain, the two groups R_(d) together with said silicon atoms and X    forming a 6- to 10-membered ring; or alternatively when Y₁ and Y₂    independently represent CR_(b)R_(c), two groups R_(b) linked to    separate carbon atoms together form a saturated hydrocarbon-based    chain, the two groups R_(b) together with the carbon atoms that bear    them and X form a 6- to 10-membered ring; and R_(f) and R_(g)    represent, independently of each other, a hydrogen atom; an alkyl    group; an acyl group; an aryl group optionally substituted with    alkyl; a cycloalkyl group optionally substituted with alkyl; an    arylalkyl group in which the aryl portion is optionally substituted    with alkyl; a halogen atom; an alkenyl group; an alkynyl group; or a    group SiG₁G₂G₃ in which G₁, G₂ and G₃ are, independently of each    other, alkyl; alkoxy; aryl optionally substituted with alkyl or    alkoxy; or arylalkyl in which the aryl portion is optionally    substituted with alkyl or alkoxy; L represents a carbene of formula    (II):    in which:    -   A and B independently represent C or N, it being understood that        when A represents N, then T₄ represents nothing, and when B        represents N, then T₃ represents nothing;    -   T₃ and T₄ independently represent a hydrogen atom; an alkyl        group; a cycloalkyl group optionally substituted with alkyl or        alkoxy; an aryl group optionally substituted with alkyl or        alkoxy; an alkenyl group; an alkynyl group; or an arylalkyl        group in which the aryl portion is optionally substituted with        alkyl or alkoxy; or alternatively    -   T₃ and T₄ may form, together with A and B when these each        represent a carbon atom, an aryl;    -   T₁ and T₂ independently represent an alkyl group; an alkyl group        optionally substituted with alkyl; a perfluoroalkyl group or an        alkyl group optionally substituted with a perfluoroalkyl group;        a cycloalkyl group optionally substituted with alkyl or alkoxy;        an aryl group optionally substituted with alkyl or alkoxy; an        alkenyl group; an alkynyl group; or an arylalkyl group in which        the aryl portion is optionally substituted with alkyl or alkoxy;        or alternatively    -   T₁ and T₂ independently represent a monovalent radical of        formula (V) below:        —V₁—V₂  (V)        in which:    -   V₁ is a divalent hydrocarbon-based radical, preferably an        optionally substituted linear or branched C₁–C₁₀ alkylene,    -   V₂ is a monovalent radical chosen from the following group of        substituents:        -   alkoxy, —OR^(v) with R^(v) corresponding to hydrogen, alkyl            or aryl        -   amine, preferably N(R^(v) )₂ with R^(v) corresponding

to hydrogen, alkyl or aryl, or alternatively

-   -   T₁ and T₂ independently represent a monovalent radical of        formula (W) below:        —W₁-ω-W₂  (W)        in which:    -   W₁ is a divalent hydrocarbon-based radical, preferably an        optionally substituted linear or branched C₁–C₁₀ alkylene,    -   ω represents:        —R^(α)C═CR^(α)—    -    with R^(α) corresponding to H or alkyl    -    or        —C≡C—    -   W₂ is a monovalent radical chosen from the following group of        substituents;        -   R^(β)=alkyl, H;        -   Si-alkyl, Si-alkenyl or Si-alkynyl, preferably Si-(alkyl)₃;        -   alcohol, preferably —C(R^(ε))₂OH with R^(ε)═H or alkyl;        -   ketone, preferably        -    with R^(δ)=alkyl; alkenyl, alkynyl;        -   carboxyl, preferably        -    with R^(δ)=alkyl; alkenyl, alkynyl;        -   amide, preferably        -    with R^(β)=H, alkyl; alkenyl, alkynyl;        -   acyl, preferably        -    with R^(δ)=alkyl; alkenyl, alkynyl;        -   or alternatively    -   the substituents T₁, T₂, T₃ and T₄ can form in pairs, when they        are located on two adjacent ring members in formula II, a        saturated or unsaturated hydrocarbon-based chain.

This process consists essentially in placing in contact:

-   -   at least one salt of formula (III):    -    in which:    -   A, B, T₁, T₂, T₃ and T₄ are as defined above;    -   Z₁, independently represents an anion derived from a Brönsted        acid (protic acid) preferably chosen from the group comprising:        -   carboxylic acids of formula Go-COOH in which Go represents            an alkyl, and advantageously a C₁–C₂₂ alkyl; an aryl,            advantageously a C₆–C₁₈ aryl optionally substituted with one            or more C₁–C₆ alkyls;        -   sulfonic acids of formula Go-SO₃H in which Go is as defined            above;        -   phosphoric acids of formula Go-PO₃H in which Go is as            defined above;        -   the following mineral acids: HF, HCl, HBr, HI, H₂SO₄, H₃PO₄,            HClO₄ and HBF₄ taken individually or in combination;        -   and mixtures thereof;    -   at least one precursor complex (IV) selected from the group of        suitable complexes comprising the complexes of formula:        Pt₂[ViMe₂Si—O—SiMe₂Vi]₃ (Karstedt complex)    -    in which Vi represents a vinyl radical;        and more generally the complexes of formula:        M₂[R₅R₆C═CR₄—Y₁—X—Y₂—CR₃═CR₁R₂]₃    -    in which M, R₅, R₆, R₄, R₃, R₁, R₂, Y₁, X and Y₂ are as defined        above, for instance:        M₂[CR₅R₆═CR₄—SiRdRe—O—SiR_(d)R_(e)—CR₃═CR₁R₂]₃, it being        understood that M, R₁, R₂, R₃, R₄, R₅, R₆, R_(d) and R_(e) are        as defined above;    -   at least one solvent (V), and    -   at least one base (VI).

One of the essential characteristics of the process according to theinvention is therefore to allow for the formation of the metal/carbenecomplex in a single step.

The procedure is thus greatly simplified. This advantage is all the moreinteresting since it is accompanied by an improvement in the yield and areduction in the cost price, without, however, affecting the applicationproperties of the metal complexes obtained. Specifically, they areselective, efficient and stable hydrosilylation catalysts that producefew isomerization and coloration side reactions.

The metallic complexes with which the process according to the inventionis concerned are defined below.

The metals of group 8 represented by M are, for example, palladium,platinum or nickel in oxidation state 0. In practice, M representsplatinum in oxidation state 0.

The term “alkyl” denotes a saturated, linear or branchedhydrocarbon-based chain, which is optionally substituted (e.g. with oneor more alkyls), preferably of 1 to 10 carbon atoms, for example 1 to 8carbon atoms and better still 1 to 7 carbon atoms.

Examples of alkyl groups are especially methyl, ethyl, isopropyl,n-propyl, tert-butyl, isobutyl, n-butyl, n-pentyl, isoamyl and1,1-dimethylpropyl.

The alkyl portion of the alkoxy radical is as defined above.

The perfluoroalkyl radical or alkyl radical optionally substituted witha perfluoroalkyl group preferably has the formula:—(CH₂)_(p—C) _(q)F_(2q+1)

in which p represents 0, 1, 2, 3 or 4; q is an integer from 1 to 10; andC_(q)F_(2q+1) is linear or branched. Preferred examples of this radicalare:—(CH₂)₂—(CF₂)₅—CF₃ and —(CF₂)₇,—CF₃.

The term “aryl” denotes a monocyclic or polycyclic and preferablymonocyclic or bicyclic, aromatic hydrocarbon-based group containing from6 to 18 carbon atoms. It should be understood that, in the context ofthe invention, the term “polycyclic aromatic radical” means a radicalcontaining two or more aromatic nuclei, which are fused (ortho-fused orortho- and peri-fused) together, i.e. having, in pairs, at least twocarbons in common.

Said aromatic hydrocarbon-based group (“aryl”) is optionallysubstituted, for example, with one or more C₁–C₃ alkyls, one or morehalohydrocarbon radicals (e.g. CF₃), one or more alkoxy (e.g. CH₃O) orone or more hydrocarbon based radicals comprising one or more ketoneunits (e.g. CH₃CO—).

Examples of aryls that may be mentioned include phenyl, naphthyl,anthryl and phenanthryl radicals.

The term “arylalkyl” denotes an alkyl group as defined above,substituted with one or more aryl groups on its hydrocarbon-based chain,the aryl group being as defined above. Examples of these are benzyl andtriphenylmethyl.

The term “acyl” means a group R_(o)—CO— in which R_(o) represents alkylas defined above; or a group Ar—CO— in which Ar represents an aryl groupas defined above, or alternatively an arylalkyl group in which aryl andalkyl are as defined above and in which the aryl portion is optionallysubstituted, e.g. with alkyl.

The term “cycloalkyl” means a monocyclic or polycyclic, preferablymonocyclic or bicyclic, saturated hydrocarbon-based radical preferablycontaining from 3 to 10 and better still from 3 to 8 carbon atoms. Theterm “saturated polycyclic hydrocarbon-based radical” means a radicalcontaining two or more cyclic nuclei attached together via σ bondsand/or fused in pairs.

Examples of polycyclic cycloalkyl groups are adamantane and norbornane.

Examples of monocyclic cycloalkyl groups are cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

The term “alkenyl” means a linear or branched, substituted orunsubstituted, unsaturated hydrocarbon-based chain containing at leastone olefinic double bond, and more preferably only one double bond. Thealkenyl group preferably contains from 2 to 8 and better still from 2 to6 carbon atoms. This hydrocarbon-based chain optionally comprises atleast one hetero atom such as O, N or S.

Preferred examples of alkenyl groups are allyl and homoallyl groups.

According to the invention, the term “alkynyl” means a linear orbranched, substituted or unsubstituted, unsaturated hydrocarbon-basedchain containing at least one acetylenic triple bond, and morepreferably only one triple bond. The alkynyl group preferably containsfrom 2 to 8 carbon atoms and better still from 2 to 6 carbon atoms.Examples that may be mentioned include the acetylenyl group and thepropargyl group. This hydrocarbon-based chain optionally comprises atleast one hetero atom such as O, N or S.

The expression “represents nothing” means that the substituents —T₃, or—T₄, respectively, are not present. Specifically, in formula (II), thenitrogen atom is trivalent, such that when A or B represents N, thenitrogen atom cannot contain an additional substituent.

The carbenes of formula (II) may contain at least two fused nuclei, i.e.at least two substituents from T₁, T₂, T₃ and T₄, located on twoadjacent ring members, together form a saturated or unsaturatedhydrocarbon-based chain preferably containing from 3 to 6 carbon atoms.The expression “saturated or unsaturated hydrocarbon-based chain” meansa linear or branched hydrocarbon-based chain, possibly containing one ormore unsaturations of olefinic double bond type or of acetylenic triplebond type.

When the carbenes (II) contain fused nuclei, they thus correspond to oneof the formulae below, in which (alk) represents a saturated orunsaturated hydrocarbon-based chain:

However, it should be understood that the carbenes II may contain morethan two fused nuclei.

The complexes that are preferably prepared by the process according tothe invention are those in which Y₁ and Y₂ either both representCR_(b)R_(c), or both represent SiR_(d)R_(e), such that said complexeshave either the formula (I.1) or the formula (I.2):

-   in which R_(b) ¹ and R_(c) ¹ are the substituents R_(b) and R_(c) of    Y₁ in formula (I.1);-   R_(b) ² and R_(c) ² are the substituents R_(b) and R_(c) of Y₂ in    formula (I.2);-   R_(d) ¹ and R_(e) ¹ are the substituents R_(b) and R_(e) of Y₁ in    formula (I.1);-   R_(d) ² and R_(e) ² are the substituents R_(d) and R_(e) of Y₂ in    formula (I.2).

Thus, R_(b) ¹ may be identical to or different than R_(b) ²; R_(c) ¹ maybe identical to or different than R_(c) ²; R_(d) ¹ may be identical toor different than R_(d) ²; and R_(e) ¹ may be identical to or differentthan R_(e) ².

In practice:R_(b) ¹═R_(b) ²; R_(c) ¹═R_(c) ²; R_(d) ¹═R_(d) ²; and R_(e) ¹═R_(e) ².R₃═R₄; R₅═R₂; and R₁═R₆.

According to one variant, R_(d) ¹ and R_(d) ² together form:

(a) either a chain:

in which n is an integer from 1 to 3; X is as defined above; and R andR′, which may be identical or different, take any of the meanings givenabove for R_(e), it being understood that, when n is 2 or 3, only onesilicon atom of said chain may be substituted with one or two alkenyl oralkynyl groups;

(b) or a saturated hydrocarbon-based chain, such that the twosubstituents R_(d), together with the two silicon atoms that bear themand X, form a 6- to 10-membered ring and preferably a 6- to 8-memberedring.

When R_(d) ¹ and R_(d) ² form the chain (a), it is preferable for n tobe 1 or 2 (better still, n is 1) and for R═R_(e), the two groups R_(e)borne by the two silicon atoms being identical. In this case, R_(e)preferably represents alkyl, for example methyl. Better still, in thesecompounds, R′ represents —CR₃═CR₁R₂ and R₁═R₆; R₅═R₂; and R₃═R₄.

When R_(d) ¹ and R_(d) ² form the chain (b), it is preferable for thetwo groups R_(d), together with the two silicon atoms and the group X,to form an 8-membered ring. In this case, it is preferable for R_(e) ¹to be identical to R_(e) ². These compounds have the general formula:

in which T represents alkyl and i is an integer between 0 and 5, T beinglocated on one or more of the ring members 1, 2, 3, 4 and 5 of the aboveformula.

Similarly, when Y₁ and Y₂ represent CR_(b)R_(c), the two groups R_(b)linked to different carbon atoms may together form a saturatedhydrocarbon-based chain (c), such that the two groups R_(b), togetherwith the carbons that bear them and X, form a 6- to 10-membered ring.Preferably, the ring formed is an 8-membered ring, in which case themetallic complex corresponds to the formula:

in which T represents alkyl; i is an integer between 0 and 5, T beinglocated on one or more of the ring members 1, 2, 3, 4 and 5 of the aboveformula.

Two groups R_(d) linked to two different silicon atoms can form a chainof formula:

When this is the case, it is preferable for X to represent O in thecompounds of the invention. These preferred compounds have the generalformula:

Among these compounds, it is preferable that R_(e) ¹═R_(e) ²Advantageously, R_(e) ¹═R_(e) ² represents alkyl (for example methyl).

Preferably, n is 1 or 2 and R═R_(e) ¹, it being understood that when nis 2, only one silicon atom of the chain O—(SiRR′—O)_(n)— can besubstituted with one or two alkenyl or alkynyl groups. Better still,R′═—CR₃═CR₁R₂ and R₁═R₆; R₂═R₅ and R₃═R₄.

When R_(f) and/or R_(g) represents SiG₁G₂G₃, it is preferable for R_(f)and/or R_(g) to be trialkylsilyl, for example SiG₁G₂G₃ in whichG₁═G₂═G₃=alkyl.

Subgroups of the metallic complexes of the invention consist ofcomplexes for which:

-   -   X=O; Y₁ and Y₂ independently represent SiR_(d)R_(e); or    -   X=NR_(a); Y₁ and Y₂ independently represent CR_(b)R_(c); or    -   X=NR_(a); Y₁ and Y₂ independently represent SiR_(d)R_(e); or    -   X=CR_(f)R_(g); Y₁ and Y₂ independently represent CR_(b)R_(c); or    -   X=CR_(f)R_(g); Y₁ and Y₂ independently represent SiR_(d)R_(e).

Among these metallic complexes of formula (I) that are preferred arethose for which:

-   -   when X represents O, Y₁ and Y₂ independently represent        SiR_(d)R_(e); or    -   when X represents NR_(a), Y₁ and Y₂ independently represent        CR_(b)R_(c); or    -   when X represents CR_(f)R_(g), Y₁ and Y₂ independently represent        CR_(b)R_(c).

In practice, X represents O and Y₁ and Y₂ independently representSiR_(d)R_(e) in the metallic complex of formula (I). In the context ofthe invention, the expression “independently represent” means that thedesignated substituents are either identical or different.

For example, R₁, R₂, R₅ and R₆ are hydrogen atoms.

Preferred meanings of R₃ and R₄ are especially a hydrogen atom; an alkylgroup; an aryl group optionally substituted with alkyl; and a cycloalkylgroup optionally substituted with alkyl. Among these preferred meaningsit is particularly advantageous for R₃ and R₄, together, to represent ahydrogen atom; (C₃–C₈)cycloalkyl or (C₁–C₈)alkyl.

For example, the diolefinic ligand of the complex of formula (I) issymmetrical, i.e. R₅═R₂; R₆═R₁; R₃═R₄ and the two groups Y₁ and Y₂ areeither strictly identical to each other, or Y₁ represents CR_(b) ¹R_(c)and Y₂═CR_(b) ²R_(c) in which R_(b) ¹ and R_(b) ² together form asymmetrical chain, or alternatively Y₁═SiR_(d) ¹R_(e) and Y₂═SiR_(d)²R_(e) in which R_(d) ¹ and R_(d) ² together form a symmetrical chain.

A preferred group of complexes according to the invention consists ofthe complexes of formula (I) in which L represents a carbene of formula(II). Preferably, A and B in the formula (II) both represent a carbonatom.

As regards the preferred embodiments of the ligands in formulae (I),(I.1) and (I.2), they are forms in which A=B=carbon atom in the formula(II) given above.

Preferred meanings for T₁ and T₂ in this formula II are:

-   -   alkyl, in particular n-propyl, n-pentyl or neopentyl        (—CH₂—C(CH₃)₃),    -   cycloalkyl, in particular cyclopentyl, cyclohexyl or adamantyl;    -   alkenyl, in particular allyl (—CH₂—CH═CH₂), or methallyl        (—CH₂—C(CH₃)═CH₂);    -   alkynyl, in particular propargyl or homopropargyl        (—(CH₂)₂—C≡CH);    -   or a monovalent radical (W) defined above, in particular        —(CH₂)—C≡C—C(CH₃)₃        γ=1 to 3        or        —(CH₂)—C≡C—Si(CH₃)₃        γ=1 to 3

Still in formula (II) and preferably, T₃ and T₄ both correspond tohydrogen or together form an aryl, and better still a phenyl.

One group of metallic complexes of formula (I) that is particularlypreferred consists of the complexes of formula:

in which:

-   T₁ and T₂ are identical and are as defined above;-   T₃ and T₄ are as defined above;-   R_(d) and R_(e) are as defined above.

According to another of its aspects, the present invention concerns, asnovel products, complexes of formula (I) in which the carbene of formula(II) is such that:

-   -   T₃ and T₄ can form, together with A and B when these each        represent a carbon atom, an aryl as defined above, preferably a        phenyl;    -   and/or T₁ and T₂ independently represent a monovalent radical of        formula (V) below:        —V₁—V₂  (V)        in which:    -   V₁ is a divalent hydrocarbon-based radical, preferably an        optionally substituted linear or branched C₁–C₁₀ alkylene,    -   V₂ is a monovalent radical chosen from the following group of        substituents:        -   alkoxy, —OR^(v) with R^(v) corresponding to hydrogen, alkyl            or aryl        -   amine, preferably N(R^(v) )₂ with R^(v) corresponding to            hydrogen, alkyl or aryl    -   or alternatively T₁ and T₂ independently represent a monovalent        radical of formula (W) below:        —W₁-ω-W₂  (W)        in which:    -   W₁ is a divalent hydrocarbon-based radical, preferably an        optionally substituted linear or branched C₁–C₁₀ alkylene,    -   ω represents:        —R^(α)C═CR^(α)—    -    with R^(α) corresponding to H or alkyl or        —C≡C—    -   W₂ is a monovalent radical chosen from the following group of        substituents:        -   R^(β)=alkyl or H;        -   Si-alkyl, Si-alkenyl or Si-alkynyl, preferably —Si(alkyl)₃;        -   alcohol, preferably —C(R^(ε))₂OH with R^(ε)=H or alkyl;        -   ketone, preferably        -    with R^(δ)=alkyl; alkenyl, alkynyl;        -   carboxyl, preferably        -    with R^(δ)=alkyl; alkenyl, alkynyl;        -   amide, preferably        -    with R^(β)=H, alkyl; alkenyl, alkynyl;        -   acyl, preferably        -    with R^(δ)=alkyl; alkenyl, alkynyl;            T₁ and T₂ preferably independently corresponding to a            radical W of the type            —(CH₂)—C≡C(CH₃)₃            γ=1 to 3            or            —(CH₂)—C≡C—Si(CH₃)₃            γ=1 to 3    -    or alternatively to one of the following units:

methyl, isopropyl, tert-butyl, n-pentyl, neopentyl, cyclopentyl,cyclohexyl, adamantyl, allyl, methallyl, propargyl or homopropargyl.

As regards the salt (III), the anion Z₁ ⁻ is the anion derived from anorganic or mineral Brönsted acid (protic acid). Usually, the anion Z₁ ⁻is derived from an acid with a pKa of less than 6. Preferably, Z₁ ⁻ isderived from an acid with a pKa of less than 4 and better still lessthan 2. The pKa values that are concerned herein are the pKa values ofthe acids as measured in water.

Examples of acids are the carboxylic acids of formula: G_(o)-COOH, inwhich G_(o) represents alkyl, for example (C₁–C₂₂)alkyl; or aryl, forexample (C₆–C₁₈)aryl optionally substituted with one or more alkyl,preferably one or more (C₁–C₆)alkyl; sulfonic acids of formula:G_(o)-SO₃H in which G_(o) is as defined above; and phosphonic acids offormula: G_(o)PO₃H in which G_(o) is as defined above; other acids areHF, HCl, HBr, HI, H₂SO₄, H₃PO₄, HClO₄ and HBF₄.

Preferred examples of carboxylic acids are acetic acid, benzoic acid andstearic acid. A preferred sulfonic acid that will be mentioned isbenzenesulfonic acid and a preferred phosphonic acid that will bementioned is phenylphosphonic acid.

According to the invention, the anions Z₁ ⁻ derived from acids HCl, HIand HBF₄ are more particularly preferred.

Thus, anions Z₁ ⁻ that are particularly preferred according to theinvention are the halide and tetrafluoroborate anions.

Precursor complexes (IV) that are suitable are especially complexes offormula:Pt₂[ViMe₂Si—O—SiMe₂Vi]₃ (Karstedt complex)

-   -    in which Vi represents a vinyl radical; and more generally the        complexes of formula:        M₂[R₅R₆C═CR₄—Y_(l)—X—Y₂—CR₃═CR₁R₂]₃    -    in which M, R₅, R₆, R₄, R₃, R₁, R₂, Y₁, X and Y₂ are as defined        above, for instance        M₂[CR₅R₆═CR₄—SiR_(d)R_(e)—O—SiR_(d)R_(e)—CR₃═CR₁R₂]₃, it being        understood that M, R₁, R₂, R₃, R₄, R₅, R₆, R_(d) and R_(e) are        as defined above.

As regards the solvent (V), it is chosen such that the solubility of thesalt (III) and of the base (VI) in said solvent (V) is at least 0.1%weight/weight at 25° C., respectively. In point of fact, in accordancewith the invention, it is preferable for the salt (III) and the base(VI) to be partially dissolved in the solvent (V).

According to one advantageous arrangement of the invention, the solvent(V) is selected from polar aprotic solvents with a boiling point at 1atm of less than 150° C. and preferably less than 120° C., preferablyfrom the group comprising:

-   -   cyclic or noncyclic ethers and in particular tetrahydrofuran        (THF), diethyl ether, diisopropyl ether, dioxane,        dimethoxyethane or diethylene glycol dimethyl ether;    -   dimethylformamide, dimethylacetamide, hexamethylphosphorylamide:        [(CH₃)₂N]₃PO and hexamethylphosphoramide [(CH₃)₂N]₃P . . . ;    -   THF being particularly preferred.

The solvent (V) must not only provide a reaction environment that isfavorable to the formation of the carbene/metal complexes, but must alsobe neutral and easy to remove.

As regards the base (VI), it is chosen as a function of its ability todeprotonate the salt (III) at least partially dissolved in the solvent(V).

It is preferably a strong base selected from the group comprising:alkali metal hydrides, alkali metal hydroxides, alkali metalcarboxylates, alkali metal alkoxides and alkali metal amides, and evenmore preferably from the group comprising:

-   -   sodium hydride, sodium methoxide, potassium tert-butoxide,        lithium diisopropylamide, and mixtures thereof.

According to one advantageous characteristic of the process according tothe invention, the concentration of the base (VI) in the reaction mediumis defined as follows [in mol/l of solvent (V)]:10⁻⁶≦VI≦10preferably 10⁻³≦VI≦1.

In quantitative terms, it is important, in accordance with theinvention, for the base (VI) not to be in an excess such that it resultsin an unwanted reaction with the constituents of the reaction mediumother than the salt III to be deprotonated.

Thus, according to a noteworthy characteristic of the invention, thesalt (III) and the base (VI) are used in amounts such that the ratioR_(VI/III) of normality VI/III is defined as follows:R _(VI/III)≦10preferably 1≦R _(VI/III)≦5and even more preferably 1≦R _(VI/III)≦3.

These consumables III, IV, V and VI are either commercially available orare readily prepared by a person skilled in the art using commercialcompounds.

A method for synthesizing the salts of formula (III) in which A=B=C isdescribed in U.S. Pat. No. 5,077,414.

This process comprises the reaction of an α,-dicarbonyl compound offormula:

in which T₃ and T₄ are as defined above, with HCHO and two amines offormulae T₁-NH₂ and T₂-NH₂ in the presence of a suitable acid. Thenature of the anion Z₁ in the salts of formula III depends on the acidused in this step. The acids that may be used are, for example, thoselisted above and from which Z₁ is derived.

Other methods for preparing the salts of formula (III) are proposed inChem. Eur. J. 1996, 2, No. 12, pages 1627–1636 and Angew. Chem. Int. Ed.Engl. 1997, 36, 2162–2187.

According to one preferred embodiment of the invention, the process thatit concerns consists essentially in:

-   -   a) dissolving the salt (III) and the compound (IV) in the        solvent (V),    -   b) incorporating the base (VI) in several portions into the        solution of (III) and (IV) in (V),    -   c) stirring the reaction medium thus prepared until compound (I)        has formed,    -   d) recovering the formed compound (I), preferably by        evaporation,    -   e) optionally, purifying,    -   f) optionally, drying.

As regards the operating conditions, it should be noted that it ispreferred to perform steps b) and c) at a temperature of between −78° C.and 50° C. and preferably at 0° C. and at atmospheric pressure.

The reaction time (steps a), b) and c)) may range, for example, from 2hours to 48 hours. It is on average 5 hours. This time decreases as thesolubility of the salt III in the medium increases. If the precursorsalt is soluble in the solvent V, the reaction time may be less than onehour.

In one even more preferred embodiment of the process according to theinvention, the following are used as starting materials introduced intothe reaction chamber:

-   -   at least one salt (III) of formula:    -    in which:        -   T₁ and T₂ are identical and represent (C₁–C₈)alkyl or            (C₃–C₈)cycloalkyl;        -   T₃ and T₄ are identical and represent hydrogen or together            represent a phenyl;        -   Z₁ is a halogen, preferably Cl or I, or BF₄;    -   at least one Karstedt complex (IV) as defined in U.S. Pat. No.        3,775,452, preferably a compound (IV) of formula:    -    in which:        -   Rd and Re are identical and represent CH₃;    -   a solvent (V) comprising THF, and    -   at least one base (VI) comprising potassium tert-butoxide        (KOt-Bu).

According to another of its aspects, the invention relates to acatalytic composition comprising, as active material, one or moremetallic complexes prepared by performing the process according to theinvention.

The catalysts thus prepared may be used in hydrosilylation reactions.They allow a homogeneous catalysis of the reaction.

A subject of the invention is thus also a hydrosilylation process and inparticular for the hydrosilylation of ethylenically and/oracetylenically unsaturated compounds, characterized in that it isperformed in the presence of a catalyst comprising the metallic complexobtained by the process described above.

For the purposes of the invention the expression “ethylenically and/oracetylenically unsaturated compounds” especially denotes organiccompounds of the olefin or acetylenic derivative type, and alsoorganomineral compounds, such as organosilicon compounds, for instancevinylsilicic and/or acetylsilicic derivatives.

According to the invention, the term “hydrosilylation reaction” meansthe reaction of a compound containing an ethylenic double bond or anacetylenic triple bond (unsaturated compound) with a compound containingat least one unit ≡Si—H so as to form a C—Si bond.

The hydrosilylation reaction may be represented schematically asfollows, in the case of a compound containing an ethylenic double bond:

and, in the case of a compound containing an acetylenic triple bond:

The compounds containing an ethylenic double bond may comprise one ormore double bonds and from 2 to 40 carbon atoms. These compounds may bealiphatic hydrocarbons with a linear or branched hydrocarbon-basedchain, or cyclic hydrocarbons, said cyclic or aliphatic hydrocarbonsoptionally bearing one or more substituents of (C₆–C₁₈)aryl typeoptionally substituted with (C₁–C₆)alkyl. The double bonds are generallyterminal.

Examples of olefins are 2-methyl-1-butene, 1-hexene, 1-heptene,1-octene, 3-ethyl-1-hexene, 1-decene, 4,4-dimethyl-1-nonene,vinylcyclohexene, styrene, 2-vinylnaphthalene, and polyorganosiloxanes(POSs) comprising at least one Si-vinyl per molecule.

The compounds containing an acetylenic triple bond may comprise one ormore triple bonds and from 2 to 40 carbon atoms. These compounds aregenerally aliphatic hydrocarbons with a linear or branchedhydrocarbon-based chain, optionally substituted with (C₃–C₁₀)cycloalkyl(which cycloalkyl may optionally bear one or more (C₁–C₆)alkyl) and/orwith (C₆–C₁₀)aryl (which aryl may optionally bear one or more(C₁–C₆)alkyl). Preferably, the compounds containing an acetylenic triplebond contain only one triple bond. The triple bonds are generallyterminal. Examples of these are: 2-propynyl, 1-propynyl and2-penten-4-ynyl.

The hydrosilylation of compounds comprising both one or more ethylenicdouble bonds and one or more acetylenic triple bonds may also beenvisaged within the context of the invention.

Under the operating conditions normally prescribed in the literature forhydrosilylation reactions, the formation of two types of hydrosilylationreaction side products is observed, namely isomerization products andhydrogenation products. The isomerization products result from theisomerization of the double bonds. The hydrogenation products resultfrom the hydrogenation of the double and triple bonds.

Surprisingly, when the hydrosilylation is performed using as catalyststhe metallic complexes prepared by the process according to theinvention, formation of these side products is greatly limited. Moreparticularly, a strong reduction in the level of isomers formed isobserved.

The hydrosilylation reaction may be performed in a solvent or in theabsence of solvent. As a variant, one of the reagents may act assolvent: for example, the compound containing an ethylenic double bondor containing an acetylenic triple bond.

Suitable solvents are solvents that are miscible with the compoundcontaining an Si—H unit.

Under the conditions of the hydrosilylation reaction, the catalyticcomplex should be dissolved in the reaction medium.

The compound containing an Si—H unit may be a silicon hydride of formula(XIII):

in which:

X is a radical comprising a hetero atom such as O, Si, a halogen atom orthe carbon atom of an aliphatic or aromatic group;

R is a hydrogen atom, an alkyl group, an aryl group, a cycloalkyl group,an alkoxy group, an aryloxy group or a cycloalkoxy group;

a is an integer from 0 to 3.

It should be understood that, according to the invention, the aliphatic,aromatic, alkyl, aryl, cycloalkyl, alkoxy, aryloxy and cycloalkoxygroups may be substituted or unsubstituted. The nature of thesubstituents is defined so as not to give rise to side reactions duringthe hydrosilylation^(reaction.)

Suitable examples of silanes are HSi(OC₂H₅)₃ and HSi(C₂H₅)₃.

The compound containing an Si—H unit may be a polymer ofpolyhydrogenosiloxane type. Other suitable polymers and copolymers arepolyhydrogenosilanes comprising a large number of repeating unitscontaining Si—H bonds.

Preferably, the polymers that may be used contain repeating units offormula:

in which X is a radical comprising a hetero atom such as O, Si or thecarbon atom of an aliphatic or aromatic group; and R_(o) is a hydrogenatom or an organic group chosen from alkyl, aryl, cycloalkyl, alkoxy,aryloxy or cycloalkoxy. Examples that may be mentioned include thepolyhydrogenosiloxanes of formula:

in which R₇ to R₁₃ are independently a hydrogen atom or an organicgroup. Preferably, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ are chosen from ahydrogen atom and an alkyl, aryl, cycloalkyl, alkoxy, aryloxy orcycloalkoxy group;

n is an integer at least equal to 1, preferably at least equal to 10 andbetter still between 10 and 100.

Suitable polymers are polymethylhydrogenosiloxanes containing —Si(CH₃)₃end groups and polydimethylsiloxanes containing —Si(CH₃)₂H end groups,methylhydrogenodimethylsiloxane copolymers containing —Si(CH₃)₂H endgroups, methylhydrogenomethyloctylsiloxane copolymers andmethylhydrogenocyclosiloxane polymers.

In general, the polymers that may be used in the reaction have anaverage molecular mass of 300 or more and preferably between 300 and 10000 (g/mol).

Examples of silicon hydrides are described in U.S. Pat. No. 5,359,113.

Examples of solvents that may be used for the hydrosilylation areespecially aliphatic hydrocarbons (such as pentane, hexane, heptane,pentamethylheptane or petroleum distillation fractions); aromatichydrocarbons (such as benzene, toluene and xylenes: ortho-xylene,para-xylene and meta-xylene); halogenated aliphatic or aromatichydrocarbons (such as tetrachloroethylene); or ethers (such astetrahydrofuran or dioxane).

The hydrosilylation reaction may be performed at a temperature ofbetween 15° C. and 300° C., for example between 20 and 240° C., betterstill between 70 and 200° C., especially between 50 and 140° C. and verypreferably between 50 and 100° C.

The relative amount of unsaturated compound and of compound containingan Si—H unit may be controlled so as to ensure the reaction of all theunsaturations with Si—H bonds.

Nevertheless, it is preferable to work in the presence of a molar excessof unsaturation.

Generally, the molar ratio of the unsaturations to the Si—H bonds rangesbetween 1:100 and 10:1.

According to the invention, the hydrosilylation reaction is performed inthe presence of a catalytic amount of one or more complexes preparedaccording to the invention. The term “catalytic amount” means less thanone molar equivalent of platinum relative to the amount of unsaturationspresent in the reaction medium.

In general, it suffices to introduce into the reaction medium less than1000 ppm, preferably less than 100 ppm and better still less than 50 ppmof platinum, calculated relative to the total mass of the unsaturatedcompound and of the compound containing Si—H units.

According to one preferred embodiment of the invention, the unsaturatedcompound, the catalyst and the solvent are stirred in a reactor. Themixture is brought to the desired temperature and the compoundcontaining Si—H units is introduced with stirring.

The invention is illustrated in the light of the examples that follow.

EXAMPLES General Features

The synthesis starting with the Karstedt complex (IV) is summarized inthe scheme below:

-   -   A, B, T₁, T₂, T₃, T₄ and Z₁ being as defined above;    -   DVTMS=divinyltetramethylsiloxane    -   KOt-Bu=potassium tert-butoxide    -   RT=room temperature

The imidazolium salt is placed in contact with the platinum complex inTHF. The addition of a strong base (potassium tert-butoxide) to thereaction mixture allows the formation of the carbene, which exchangesrapidly with one of the olefins complexed to the metal to give thecorresponding platinum-carbene.

The reaction yields and selectivity are good. In addition, this processis advantageous as a result of its ease of implementation.

Example 1

Scale: 1.8 mmol Glassware: 200 ml round-bottomed flask Magnetic stirringAdditions:

-   -   4.97 grams of a Karstedt solution containing 16.1% of platinum,        i.e. 4.1 mmol of platinum,    -   1.31 g of N,N-di(cyclohexyl)imidazolium tetrafluoroborate, i.e.        4.1 mmol (A=B=C; T₃=T₄=H, T₁=T₃=cyclohexyl), prepared according        to the method described in Chem. Eur. J. 1996, 2, No. 12, pages        1627–1636 and Angew. Chem. Int. Ed. Engl. 1997, 36, 2162–2187,    -   926 mg of potassium tert-butoxide, i.e. 8.2 mmol (2 equiv.),    -   100 mL of dry THF.

The solution of Karstedt complex and the imidazolium salt are dissolvedin the THF. The potassium tert-butoxide is added over one hour at 0° C.and the mixture is stirred for five hours. The reaction medium isconcentrated under vacuum. The residue is taken up in 30 ml ofdichloromethane. This organic phase is then washed with three times 20ml of water and then twice 20 ml of saturated NaHCO₃ solution. Theorganic phase is recovered and then concentrated under vacuum. The solidresidue is then washed with three times 2 ml of ethanol. 1.8 g of ananalytically pure white solid are thus obtained (71% yield).

Example 2

Scale: 1.0 mmol Glassware: 100 ml round-bottomed flask Magnetic stirringAdditions:

-   -   1.20 grams of a Karstedt solution containing 16.2% platinum,        i.e. 1 mmol of platinum,    -   268 mg of N,N-di(t-butyl)imidazolium tetrafluoroborate, i.e. 1        mmol (1.0 equiv.) (A=B=C; T₃=T₄=H, T₁=T₂=t-butyl),    -   240 mg of potassium tert-butoxide, i.e. 2 mmol (2 equiv.),    -   80 ml of dry THF.

The solution of the Karstedt complex and the imidazolium salt arediluted in 80 ml of THF. The potassium tert-butoxide is added at roomtemperature and the mixture is stirred for 10 hours in the absence oflight. The reaction medium is evaporated and the solid obtained ispurified by rapid filtration through silica gel (eluent: H₂Cl₂). Afterevaporating off the solvent, the mixture is rinsed with two millilitersof hexamethyldisiloxane and then dried under vacuum. 640 mg of ananalytically pure white solid are obtained (98% yield).

Example 3

Scale: 0.5 mmol Glassware: 50 ml round-bottomed flask Magnetic stirringAdditions:

-   -   0.6 gram of a Karstedt solution containing 16.2% platinum, i.e.        0.5 mmol of platinum,    -   137 mg of N,N-dimethylbenzimidazolium iodide, i.e. 0.5 mmol (1.        0 equiv.) (A,B,T₃,T₄=benzyl; T₁=T₂=methyl),    -   112 mg of potassium tert-butoxide, i.e. 1 mmol (2 equiv.)    -   20 ml of dry THF.

The solution of the Karstedt complex and the benzimidazolium salt areplaced in the round-bottomed flask and then diluted in 20 ml of THF. Thepotassium tert-butoxide is added at room temperature and the mixture isstirred for 36 hours in the absence of light. The reaction medium isdiluted in dichloromethane and then washed with water. The solvent isevaporated off and the oil obtained is rapidly filtered through silicagel (eluent: CH₂Cl₂). After evaporating off the solvent, the solidobtained is rinsed with two milliliters of hexamethyldisiloxane. 173 mg(66% yield) of an analytically pure white solid are obtained.

1. A process for preparing metallic complexes of formula (I):

in which: M represents a metal selected from the metals of group 8 ofthe Periodic Table as published in the Handbook of Chemistry andPhysics, 65th Edition, 1984–1985; X represents O, NR_(a) or CR_(f)R_(g);Y₁ and Y₂ represent, independently of each other, CR_(b)R_(c) orSiR_(d)R_(e); R₁, R₂, R₃, R₄, R₅, R₆, R_(a), R_(b) and R_(c), which maybe identical or different, are selected from a hydrogen atom; an alkylgroup; an acyl group; an aryl group optionally substituted with alkyl; acycloalkyl group optionally substituted with alkyl; and an arylalkylgroup in which the aryl portion is optionally substituted with alkyl;R_(d) and R_(e) are independently chosen from alkyl; aryl optionallysubstituted with alkyl; cycloalkyl optionally substituted with alkyl;and arylalkyl in which the aryl portion is optionally substituted withalkyl; or alternatively when Y₁ and Y₂ independently representSiR_(d)R_(e), two groups R_(d) linked to two separate silicon atomstogether form a chain of formula:

in which n is an integer from 1 to 3; X is as defined above; R and R′,which may be identical or different, take any of the meanings givenabove for R_(e), it being understood that, when n is 2 or 3, only onesilicon atom of said chain may be substituted with one or two alkenyl oralkynyl groups; or alternatively when Y₁ and Y₂ independently representSiR_(d)R_(e), two groups R_(d) linked to separate silicon atoms togetherform a saturated hydrocarbon-based chain, the two groups R_(d) togetherwith said silicon atoms and X forming a 6- to 10-membered ring; oralternatively when Y₁ and Y₂ independently represent CR_(b)R_(c), twogroups R_(b) linked to separate carbon atoms together form a saturatedhydrocarbon-based chain, the two groups R_(b) together with the carbonatoms that bear them and X form a 6- to 10-membered ring; and R_(f) andR_(g) represent, independently of each other, a hydrogen atom; an alkylgroup; an acyl group; an aryl group optionally substituted with alkyl; acycloalkyl group optionally substituted with alkyl; an arylalkyl groupin which the aryl portion is optionally substituted with alkyl; ahalogen atom; an alkenyl group; an alkynyl group; or a group SiG₁G₂G₃ inwhich G₁, G₂ and G₃ are; independently of each other, alkyl; alkoxy;aryl optionally substituted with alkyl or alkoxy; or arylalkyl in whichthe aryl portion is optionally substituted with alkyl or alkoxy; Lrepresents a carbene of formula (II):

in which: A and B independently represent C or N, it being understoodthat when A represents N, then T₄ represents nothing, and when Brepresents N, then T₃ represents nothing; T₃ and T₄ independentlyrepresent a hydrogen atom; an alkyl group; a cycloalkyl group optionallysubstituted with alkyl or alkoxy; an aryl group optionally substitutedwith alkyl or alkoxy; an alkenyl group; an alkynyl group; or anarylalkyl group in which the aryl portion is optionally substituted withalkyl or alkoxy; or alternatively T₃ and T₄ may form, together with Aand B when these each represent a carbon atom, an aryl; T₁ and T₂independently represent an alkyl group; an alkyl group optionallysubstituted with alkyl; a perfluoroalkyl group or an alkyl groupoptionally substituted with a perfluoroalkyl group; a cycloalkyl groupoptionally substituted with alkyl or alkoxy; an aryl group optionallysubstituted with alkyl or alkoxy; an alkenyl group; an alkynyl group; oran arylalkyl group in which the aryl portion is optionally substitutedwith alkyl or alkoxy; or alternatively T₁ and T₂ independently representa monovalent radical of formula (V) below:—V₁—V₂  (V) in which: V₁ is a divalent hydrocarbon-based radical,optionally substituted linear or branched C₁–C₁₀ alkylene, V₂ is amonovalent radical chosen from the following group of substituents:alkoxy, —OR^(v) with R^(v) corresponding to hydrogen, alkyl or arylamine, preferably N(R^(v))₂ with R^(v) corresponding to hydrogen, alkylor aryl, or alternatively T₁ and T₂ independently represent a monovalentradical of formula (W) below:—W₁—ω—W₂  (W) in which: W₁ is a divalent hydrocarbon-based radical,preferably an optionally substituted linear or branched C₁–C₁₀ alkylene,ω to represents:—R^(α)C═CR^(α)—  with R_(α) corresponding to H or alkyl  or—C≡C— W₂ is a monovalent radical selected from the following group ofsubstituents: R^(β)=alkyl, H; Si-alkyl, Si-alkenyl or Si-alkynyl,preferably Si-(alkyl)₃; alcohol, preferably —C(R^(ε))₂OH with R^(ε)=OH,H or alkyl; ketone, preferably

 with R^(δ)=alkyl; alkenyl, alkynyl; carboxyl, preferably

 with R^(δ)=alkyl; alkenyl, alkynyl; amide, preferably

 with R^(β)=H, alkyl; alkenyl, alkynyl; acyl, preferably

 with R^(δ)=alkyl; alkenyl, alkynyl; or alternatively the substituentsT₁, T₂, T₃ and T₄ can form in pairs, when they are located on twoadjacent ring members in formula II, a saturated or unsaturatedhydrocarbon-based chain; this process comprising placing in contact: atleast one salt of formula (III):

 in which: A, B, T₁, T₂, T₃ and T₄ are as defined above; Z₁independently represents an anion derived from a Brönsted acid (proticacid) selected from the group comprising: carboxylic acids of formulaGo-COOH in which Go represents an alkyl, and optionally a C₁–C₂₂ alkyl;an aryl, optionally a C₆–C₁₈ aryl optionally substituted with one ormore C₁–C₆ alkyls; sulfonic acids of formula Go-SO₃H in which Go is asdefined above; phosphoric acids of formula Go-PO₃H in which Go is asdefined above; the following mineral acids: HF, HCl, HBr, HI, H₂SO₄,H₃PO₄, HClO₄ and HBF₄ taken individually or in combination; and mixturesthereof; at least one precursor complex (IV) selected from the group ofsuitable complexes comprising the complexes of formula:Pt₂[ViMe₂Si—O—SiMe₂Vi]₃ (Karstedt complex) in which Vi represents avinyl radical; and more generally the complexes of formula:M₂[R₅R₆C═CR₄—Y₁—X—Y₂—CR₃═CR₁R₂]₃ in which M, R₅, R₆, R₄, R₃, R₁, R₂, Y₁,X and Y₂ are as defined above, for instance:M₂[CR₅R₆═CR₄—SiR_(d)R_(e)—O—SiR_(d)R_(e)—CR₃═CR₁R₂]₃, it beingunderstood that M, R₁, R₂, R₃, R₄, R₅, R₆ and R_(e) are as definedabove; at least one solvent (V), and at least one base (VI).
 2. Theprocess as claimed in claim 1, wherein the compound of formula (I) isobtained in a single step.
 3. The process as claimed in claim 1, whereinthe solvent (V) is chosen such that the solubility of the salt (III) andof the base (VI) in said solvent (V) is at least 0.1% weight/weight at25° C., respectively.
 4. The process as claimed in claim 1, wherein thesolvent (V) is selected from polar aprotic solvents with a boiling pointat 1 atm of less than 150° C. comprising: cyclic or noncyclic ethers andin particular tetrahydrofuran (THF), diethyl ether, diisopropyl ether,dioxane, dimethoxyethane or diethylene glycol dimethyl ether;dimethylformaxnide, dimethylacetamide, hexamethylphosphorylamide:[(CH₃)₂N]₃PO and hexamethylphosphoramide [(CH₃)₂N]₃P.
 5. The process asclaimed in claim 1, wherein the base(s) (VI) is (are) selected fromstrong bases capable of deprotonating the salt (III) from the groupcomprising: alkali metal hydrides, alkali metal hydroxides, alkali metalcarboxylates, alkali metal alkoxides and alkali metal amides, and evenmore preferably from the group comprising: sodium hydride, sodiummethoxide, potassium tertbutoxide, lithium diisopropylamide, andmixtures thereof.
 6. The process as claimed in claim 1, wherein theconcentration of the base (VI) in the reaction medium, in M/1 of solvent(V), is:10⁻⁶≦VI≦10.
 7. The process as claimed in claim 1, wherein the salt (III)and the base (VI) are used in amounts such that the ratio R_(VI/III) ofnormality VI/III is defined as follows:R _(VI/III)≦10.
 8. The process as claimed in claim 1, comprising: a)dissolving the salt (III) and the compound (IV) in the solvent (V), b)incorporating the base (VI) in several portions into the solution of(III) and (IV) in (V), c) stirring the reaction medium thus prepareduntil compound (I) has formed, d) recovering the formed compound (I),preferably by evaporation, e) purifying, f) drying.
 9. The process asclaimed in claim 1, wherein steps b) and c) are performed at atemperature of between −78° C. and 50° C.
 10. The process as claimed inclaim 1, wherein the following are used: at least one salt (III) offormula:

 in which: T₁ and T₂ are identical and represent (C₁–C₈)alkyl or (C₃–C₈)cycloalkyl; T₃ and T₄ are identical and represent hydrogen or togetherrepresent a phenyl; Z₁ is a halogen; at least one Karstedt complex (IV),optionally a compound (IV) of formula:

 in which: Rd and Re are identical and represent CH₃; a solvent (V)comprising THF, and at least one base (VI) comprising potassiumtertbutoxide (KOt-Bu).
 11. A process for the hydrosilylation ofethylenically and/or acetylenically unsaturated compounds, which isperformed in the presence of a catalyst comprising the metallic complexobtained by the process as claimed in claim 1.